Brown Ring Patch, Polyoxin-D & Savage Pathology Style Q&A

Sorry for barging in on Megan's Friday posting but better late than never :)

Brown Ring Patch on Creeping Bentgrass in Arizona?
Gabe Towers (Target Specialty Products) in Arizona sent these pictures in from a creeping bentgrass green at a course outside of Phoenix. According to his observations, it's definitely a Rhizoctonia-type disease and the mycelia and symptoms look an awful lot like what we would expect brown ring patch to look like on bentgrass. Unlike the bright yellow rings associated with the disease on annual and rough bluegrass, brown ring patch on bentgrass makes nice brown sunken rings. These symptoms are like those first described for the disease orginally in Japan on this turf type.








































One of the things that we're seeing here is also the development of patches without rings. Although rings are typically seen with the disease, we did isolate Waitea circinata var. circinata from similar patches in Idaho last year.

The most compelling evidence for brown ring patch would be the presence of aeial mycelium after incubation plus the sunken degraded thatch on the greens.

We're working with Gabe right now to confirm the pathogen identity, but if it is brown ring patch, that'd be a first for the disease on creeping bentgrass in Arizona.

Polyoxin-D: Soon Available in Two Fruity Flavors!
Well, not really. Polyoxin-D fungicides kind of smells like Top Ramen to me. Polyoxin-D has proven to be one of the best fungicides for brown ring patch control and will soon be available from two companies in 2010. There's a little bit of a backstory on this one, but I'll skip the details and just say that two formulations from two different companies will be available soon.

Endorse 2.5WP is now part of Arysta's line of turf fungicides. It was previously marketed and distributed by Cleary Chemical, and we should expect no major changes to the label and the use rate will continue to be at 4 oz per 1,000 sq ft.

Cleary Chemical will now be selling Affirm 11.3WDG. This has about 4x more polyoxin-D than Endorse, so the expected use rate will be 1 oz per 1,000 sq ft.

For more information (as it becomes available) please see the maunfacturer websites:
http://www.arystalifescience.com
http://www.clearychemical.com

Question of the Week
This is kind of a new feature for the Left Coast blog, but inspired by columns such as Dear Abby, Car Talk, and Savage Love, and the slow down of info this winter, I'm going to try to post Q&As recieved by email.

Hi Frank,

I am looking for a third product for snow mold control on poa greens (monterey peninsula). My curent rotation is Instrata followed by Chipco GT every 14 to 21 days depending on the disease pressure. I was considering Eagle in combo with Fore any thoughts?

Thanks in advance,
Moldy in Monterey


Dear Moldy -

Pink snow mold in California can be tricky since it can fire at cold (< 65F daytime temps) and wet conditions without snowfall. As you know, it can go from 50 to 80F in a week in parts of California during the winter, especially in southern California, making this disease somewaht unpredictable. As such, creating a clear, defined pink snow mold (aka Microdochium patch) preventive fungicide program can be dififcult and often superintendents end up making a lot of curative applications for this disease. Please look at page 16 from Paul Vincelli's (University of Kentucky) overview of turf fungicides - the ratings are based on the average of trials performed for the last 10 or so years over all of the US.

www.ca.uky.edu/agc/pubs/ppa/ppa1/ppa1.pdf

Can you use PCNB? If you consistently stay below 70F during the winter - PCNB is really useful - long lasting, no resistance, cheap - but, if it goes over 70F, you can potentially get burn and or root pruning at high rates. Maybe target PCNB apps for the coldest part of the year , saving your Instrata applications for times when temps can get warmer.

Since Instrata = Banner + Medallion + Daconil, Medallion and Daconil are probably limited as alternate rotation partners due to label rate limitations.

You can use another DMI (Banner, Eagle, etc..) in the rotation since DMI resistance really hasn't been an issue for pink snow mold yet - but as you can see from Paul's chart, some DMIs work better than others. It'd probably be a good idea to mix this application with something else for added protection. As you indicated, mancozeb (Fore) is a good choice in your case.

I think the QoIs (Heritage, Compass, Insignia, Disarm) can be dicey for snow mold control; we've seen a few cases of resistance in CA, but this topic needs a lot more research. Thiophanate-methyl should be used with caution, resistance has been around in WA since the 1980s.

Finally, good call on the Chipco 26GT as a rotation partner. Since tolerance may be an issue in some places, keep the rates on the higher end or mixing with a contact such as mancozeb in your rotation may help.

How's that sound?

Thanks,
Frank

That's it for this week. Signing off from the Left Coast.....